Conventional imagers suffer from shortcomings with respect to the quality of data they can produce. For example, a typical imager has limited spatial resolution and has limited dynamic range for measuring the brightness, color, and polarization of light. For example, conventional cameras can have spatial resolution as low as 640×480 pixels, and color resolution as low as 8 bits. Furthermore, most non-stereoscopic imagers are unable to measure scene depth—i.e., the distance between the imager and the object being imaged. Such limitations render many conventional imagers inadequate for certain computational vision tasks such as, for example, feature detection, object recognition, motion measurement, and scene reconstruction.
Efforts have been made to enhance the quality of image data generated by video and still cameras. For example, in order to enhance the resolution and dynamic range of image data, and/or to provide additional information such as polarization data, it is possible to record multiple images of the same scene, each image taken under a different camera configuration. In one such technique, illustrated in FIG. 21, a filter wheel 2104 containing several different optical filters 2106 is mounted in front of the objective lens 2102 of a camera 2108. Each of the filters 2106 has a different optical characteristic such as a particular intensity reduction factor, spectral filtering characteristic, polarization filtering characteristic, or other optical characteristic. Each image is recorded using a different filter 2106. Between images the filter wheel 2104 is rotated about an axis of rotation 2110.
However, such a filtering technique tends to be cumbersome, because the filters 2106 must be sufficiently large to cover the field of view of the camera 2108. This requirement makes the filter wheel 2104 bulky and heavy, and therefore, a substantial amount of energy is required to move the filter wheel 2104 between frames. As a result, the frame rate of the system tends to be too slow for real-time imaging. In addition, such an arrangement requires each image to be recorded through a single filter 2106, and therefore, the switching of the filters 2106 must be synchronized with the image frames. The limited speed at which the filters 2106 can be switched thus reduces the rate at which images can be captured. Furthermore, synchronization requires additional timing circuitry.